check or replace cap and rotor if they are old at all. 4.3L are bad about eating caps and rotors and it causes all kinds of issues.
check the pink and white wires from the coil to the distrib they like to break inside the insulation where you cant tell and it will cause no fuel injection and no spark both i have found out in the past. mess around with them while cranking or running and see if it changes anything.
took me a year to figure this one out the first time on a 92 4.3L we had that randomly wouldnt start or would randomly die, we replaced everything only to find out it was the pink wire of this short harness the whole time!
make sure the distributor is set to zero also
bad ground is not a common issue on these, but its worth checking them sure.
fuel pump death syndrome is extremly common on these along with the bad cap and rotor syndrome
these two and the coil primary wires is where i would be looking